Calorimetric characterization of surface reactivity of supported Ga2O3 catalysts

The surface properties of supported gallium oxide catalysts prepared by imp regnation of various supports (gamma -Al2O3, SiO2, TiO2, ZrO2) were investi gated by adsorption microcalorimetry, using ammonia and water as probe mole cules. In the case of acidic supports (gamma -Al2O3, ZrO2, TiO2), the acidi c character of supported gallium catalysts always decreased in comparison w ith gallium-free supports; on very weakly acidic SiO2, new acidic centers w ere created when depositing Ga2O3. The addition of gallium oxide decreased the hydrophilic properties of alumina, titania and zirconia, but increased the amount of water adsorbed on silica. The catalytic performances in the s elective catalytic reduction of NO by C2H4 in excess oxygen were in the ord er Ga/Al2O3> Ga/TiO2> Ga/ZrO2> > Ga/SiO2. This order is more related to the quality of the dispersion of Ga2O3 on the support than to the global acidi ty of the solids.